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Milky Way
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Milky Way May Be Much Larger Than Previously Estimated

The Milky Way galaxy is at least 50 percent larger than is commonly estimated, according to new findings that reveal that the galactic disk is contoured into several concentric ripples. The research, conducted by an international team led by Rensselaer Polytechnic Institute Professor Heidi Jo Newberg, revisits astronomical data from the Sloan Digital Sky Survey which, in 2002, established the presence of a bulging ring of stars beyond the known plane of the Milky Way.
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Corrugation of the Milky Way Galaxy

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Rings and Radial Waves in the Disk of the Milky Way

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Title: The observed spiral structure of the Milky Way
Author: L. G. Hou, J. L. Han

The spiral structure of the Milky Way is not yet well determined. The keys to understanding this structure are to increase the number of reliable spiral tracers and to determine their distances as accurately as possible. HII regions, giant molecular clouds (GMCs), and 6.7-GHz methanol masers are closely related to high mass star formation, and hence they are excellent spiral tracers. We update the catalogs of Galactic HII regions, GMCs, and 6.7-GHz methanol masers, and then outline the spiral structure of the Milky Way. We collected data for more than 2500 known HII regions, 1300 GMCs, and 900 6.7-GHz methanol masers. If the photometric or trigonometric distance was not yet available, we determined the kinematic distance using a Galaxy rotation curve with the current IAU standard, R_0 = 8.5 kpc and Theta_0 = 220 km s-1, and the most recent updated values of R_0 = 8.3 kpc and Theta_0 = 239 km s-1, after we modified the velocities of tracers with the adopted solar motions. With the weight factors based on the excitation parameters of HII regions or the masses of GMCs, we get the distributions of these spiral tracers. The distribution of tracers shows at least four segments of arms in the first Galactic quadrant, and three segments in the fourth quadrant. The Perseus Arm and the Local Arm are also delineated by many bright HII regions. The arm segments traced by massive star forming regions and GMCs are able to match the HI arms in the outer Galaxy. We found that the models of three-arm and four-arm logarithmic spirals are able to connect most spiral tracers. The four-arm model provides a better match to the observed tangential directions of spiral arms, and is consistent with the two-fold symmetry of the Galaxy structure. A model of polynomial-logarithmic spirals not only delineates the tracer distribution but also matches the observed tangential directions.

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Astronomers weigh up Milky Way

The Milky Way is lighter than astronomers previously thought, researchers have concluded.
A team of scientists led by the University of Edinburgh found it has about half the mass of a neighbouring galaxy, known as Andromeda.
Their estimates come from working out the mass of invisible matter found in the outer regions of both galaxies.
They concluded that dark matter accounted for Andromeda's extra weight.

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Title: The starbursts in the Milky Way
Author: Ignacio Negueruela (Alicante)

High-mass stars are major players in the chemical and dynamical evolution of galaxies, and young massive clusters are the natural laboratories to study their evolution and their impact on star formation processes. Only in recent years have we become aware of the existence of numerous massive (M_cl > 10000M_sun) clusters in our Galaxy. Here I give a review, rather biased towards my own research interests, of the observational and theoretical efforts that have led to a description of their properties, and present an overview of the two (perhaps three) starburst regions known outside the Galactic Centre neighbourhood: the Scutum Complex, its putative counterpart on the far side of the Long Bar, and the starburst cluster Westerlund 1.

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Gaia-ESO data show Milky Way may have formed 'inside-out', and provide new insight into Galactic evolution

A breakthrough using data from the Gaia-ESO project has provided evidence backing up theoretically-predicted divisions in the chemical composition of the stars that make up the Milky Way's disc - the vast collection of giant gas clouds and billions of stars that give our Galaxy its 'flying saucer' shape.
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Massive stars mark out Milky Way's 'missing' arms

A 12-year study of massive stars has reaffirmed that our Galaxy has four spiral arms, following years of debate sparked by images taken by NASAs Spitzer Space Telescope that only showed two arms.
The new research, which is published online today [17 December] in the Monthly Notices of the Royal Astronomical Society, is part of the RMS Survey, which was launched by academics at the University of Leeds.

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A survey from Herschel has revealed that the reservoir of molecular gas in the Milky Way is hugely underestimated - almost by one third - when it is traced with traditional methods. Monitoring the emission from ionised carbon, the new study identified molecular gas in the intermediate evolutionary stage between diffuse, atomic gas and the densest star-forming molecular clouds. The discovery not only indicates that there is more raw material for the formation of new stars in the Galaxy, but also that it extends farther than astronomers knew.
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Local Arm
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Milky Way's 'Local Arm' larger than thought

Our home in the Milky Way galaxy could be much larger than previously thought, a new study suggests.
Earth resides between two major spiral arms of our home galaxy, in a structure called the Local Arm.
New research using the ultra-sharp radio vision of the National Science Foundation's Very Long Baseline Array (VLBA) indicates that the Local Arm, previously thought to be only a small spur, instead is much more like the adjacent major arms, and is likely a significant branch of one of them.

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RE: Milky Way
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Title: The spiral structure of our Milky Way
Authors: L. G. Hou, J. L. Han

The spiral structure of our Milky Way has not yet been well outlined. HII regions, giant molecular clouds (GMCs) and 6.7-GHz methanol masers are primary tracers for spiral arms. We collect and update the database of these tracers which has been used in Hou, Han & Shi (2009) for mapping the spiral structure.

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ALMA Detects Signs of Star Formation Surprisingly Close to Galaxy's Supermassive Black Hole

Astronomers using the Atacama Large Millimetre/submillimetre Array (ALMA) have discovered signs of star formation perilously close to the supermassive black hole at the center of the Milky Way Galaxy. If confirmed, this would be the first time that star formation was observed so close to the galactic center.
The center of our galaxy, 27,000 light-years away in the direction of the constellation Sagittarius, is home to a monstrous black hole with a mass of four million suns. Extending outward from this gravitational behemoth for many light-years is a turbulent region of space that is thought to be wracked by such extreme tidal forces that any star-forming clouds of dust and gas would be stretched thin and shredded long before infant stars could emerge.

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